diff options
Diffstat (limited to 'lib/unicode.ml')
| -rw-r--r-- | lib/unicode.ml | 77 |
1 files changed, 76 insertions, 1 deletions
diff --git a/lib/unicode.ml b/lib/unicode.ml index 0dc4238ee..dc852d981 100644 --- a/lib/unicode.ml +++ b/lib/unicode.ml @@ -18,7 +18,7 @@ exception Unsupported to simplify the masking process. (This choice seems to be a good trade-off between speed and space after some benchmarks.) *) -(* A 256ko table, initially filled with zeros. *) +(* A 256 KiB table, initially filled with zeros. *) let table = Array.make (1 lsl 17) 0 (* Associate a 2-bit pattern to each status at position [i]. @@ -147,6 +147,11 @@ let utf8_of_unicode n = s end +(* If [s] is some UTF-8 encoded string + and [i] is a position of some UTF-8 character within [s] + then [next_utf8 s i] returns [(j,n)] where: + - [j] indicates the position of the next UTF-8 character + - [n] represents the UTF-8 character at index [i] *) let next_utf8 s i = let err () = invalid_arg "utf8" in let l = String.length s - i in @@ -256,3 +261,73 @@ let ascii_of_ident s = (Buffer.add_char out s.[!i]; incr i) done; Buffer.contents out + +(* Compute length of an UTF-8 encoded string + Rem 1 : utf8_length <= String.length (equal if pure ascii) + Rem 2 : if used for an iso8859_1 encoded string, the result is + wrong in very rare cases. Such a wrong case corresponds to any + sequence of a character in range 192..253 immediately followed by a + character in range 128..191 (typical case in french is "déçu" which + is counted 3 instead of 4); then no real harm to use always + utf8_length even if using an iso8859_1 encoding *) + +(** FIXME: duplicate code with Pp *) + +let utf8_length s = + let len = String.length s + and cnt = ref 0 + and nc = ref 0 + and p = ref 0 in + while !p < len do + begin + match s.[!p] with + | '\000'..'\127' -> nc := 0 (* ascii char *) + | '\128'..'\191' -> nc := 0 (* cannot start with a continuation byte *) + | '\192'..'\223' -> nc := 1 (* expect 1 continuation byte *) + | '\224'..'\239' -> nc := 2 (* expect 2 continuation bytes *) + | '\240'..'\247' -> nc := 3 (* expect 3 continuation bytes *) + | '\248'..'\251' -> nc := 4 (* expect 4 continuation bytes *) + | '\252'..'\253' -> nc := 5 (* expect 5 continuation bytes *) + | '\254'..'\255' -> nc := 0 (* invalid byte *) + end ; + incr p ; + while !p < len && !nc > 0 do + match s.[!p] with + | '\128'..'\191' (* next continuation byte *) -> incr p ; decr nc + | _ (* not a continuation byte *) -> nc := 0 + done ; + incr cnt + done ; + !cnt + +(* Variant of String.sub for UTF8 character positions *) +let utf8_sub s start_u len_u = + let len_b = String.length s + and end_u = start_u + len_u + and cnt = ref 0 + and nc = ref 0 + and p = ref 0 in + let start_b = ref len_b in + while !p < len_b && !cnt < end_u do + if !cnt <= start_u then start_b := !p ; + begin + match s.[!p] with + | '\000'..'\127' -> nc := 0 (* ascii char *) + | '\128'..'\191' -> nc := 0 (* cannot start with a continuation byte *) + | '\192'..'\223' -> nc := 1 (* expect 1 continuation byte *) + | '\224'..'\239' -> nc := 2 (* expect 2 continuation bytes *) + | '\240'..'\247' -> nc := 3 (* expect 3 continuation bytes *) + | '\248'..'\251' -> nc := 4 (* expect 4 continuation bytes *) + | '\252'..'\253' -> nc := 5 (* expect 5 continuation bytes *) + | '\254'..'\255' -> nc := 0 (* invalid byte *) + end ; + incr p ; + while !p < len_b && !nc > 0 do + match s.[!p] with + | '\128'..'\191' (* next continuation byte *) -> incr p ; decr nc + | _ (* not a continuation byte *) -> nc := 0 + done ; + incr cnt + done ; + let end_b = !p in + String.sub s !start_b (end_b - !start_b) |